1. Field of the Invention
The present invention relates to an apparatus and method for depositing molecular impurities on a semiconductor wafer, and more particularly, to an apparatus that can quantitatively deposit expected molecular impurities on a semiconductor wafer so as to trace the cause of a defective semiconductor device.
2. Description of the Related Art
In the process steps for fabricating a semiconductor device, it is very important to optimally control molecular impurities because the molecular impurities within the clean room cause many problems and can exert a harmful influence upon the semiconductor device, which has a high degree of integration.
In a clean room, a secondary air current is generated by the movement of many items, such as production facilities, measuring instruments, produced devices, workers, robots for production, an unbalance of a spacial temperature, and so on. Because particles (i.e., fine dusts) adjacent to the moving objects are moved due to the secondary air current, wafers may be contaminated with the moving particles. It is thus important to remove such particles in the clean room to enhance the productivity of the semiconductor devices fabricated therein.
In addition, as the process steps for fabricating a semiconductor device become more complicated and take longer to complete, the wafers are contaminated more and more. The particles on wafers generate electric charges or cause crystallization defects.
Furthermore, since particles are accumulated from one another, the production device yield is influenced by a very small amount of contamination source. Therefore, it is necessary to trace the cause of several defective semiconductor devices, analyse the defective mechanism, and predetermine a contamination control level and a process limitation caused by the contamination source.